Annet was Governor of French Somaliland from 1935 to 1937. He was Lieutenant-Governor of Dahomey from 1938 to 1940. In 1940, Annet sided with Vichy France after the Fall of France.
As the Vichy Governor-General of Madagascar from 1941 to 1942, Annet was involved in the Battle of Madagascar.
On 5 November 1942, Annet surrendered his remaining forces near Ihosy, on the south of the island. Annet died in Paris.
Starting on 5 May 1942, he defended the island with about 8,000 troops.